Water, Water, Everywhere: A Profile of Water Purification Systems - The Scientist - Magazine of the Life Sciences

Date: June 8, 1998 Author: Michael BrushPoint of Use Water Filtration Systems He was described as a "grey-beard loon," but the superstitious old sailor of Samuel Taylor Coleridge's The Rime of the Ancient Mariner clearly understood the value of a reliable and consistent source of pure water. Trapped on a ship becalmed in the doldrums and faced with an exhausted fresh water supply, the old sailor lamented, "Water, water, everywhere, nor any drop to drink." The pure water requirements of the modern life science lab are just as important as the fresh water needs of the old sailor. The convenience of obtaining as much water as needed at a moment's notice, free from worries about possible contaminants, can't be beat. In this profile, Labconsumer looks at point-of-use water purification systems that produce reagent grade, Type I water directly in the laboratory The production of Type I water involves the successful removal of a variety of impurities and contaminants. These are generally lumped into the following groups. Particulate matter: This includes suspended particles, such as silt, sand, and clay particles, ranging between 1 micron and 20 microns in size, and colloidal particles, which fall between 0.01 micron and 1.0 micron in size. Altogether, these particles cause water to appear unclear or cloudy. Microorganisms: Bacteria, protozoa, viruses, and algae are among the organisms that contaminate water. Microorganisms give rise to pyrogens, which are thermostable, lipopolysaccharide fragments of cell walls. Pyrogens cause immune responses such as fevers when injected into mammals, and hinder...